Published by M+R and the Nonprofit Technology Network, the 10th annual report analyzed 105 nonprofits of various sizes and sectors, 2.8 billion emails, and 69.4 million subscribers.

The study revealed that online revenue grew by 19 percent last year, up from a 12 percent growth in 2014. Monthly giving, which the study shows is growing faster than one-time giving, accounted for 17 percent of all online revenue.

Email open rates, click-through rates and response rates all declined in 2015; however, email fundraising grew 25 percent, accounting for 29 percent of all online revenue for the year. The report says that continuing list growth and volume (more people; more messages) explain the increase in email revenue despite the fall in email engagement. For every 1,000 fundraising email delivered last year, nonprofits received $44 in donations, an average of $0.44 cents for every email. Groups sent an average of 49 messages in 2015.

The study showed that of the $481 million in online donation raised by leading nonprofits last year, 13 percent were made from mobile devices.

And although social media is an important tool for nonprofits, many organizations are not allocating as much of their resources to social strategies as they should. The top 25 organizations with the largest online revenue growth invested $0.12 in digital advertising for every dollar raised online; the rest of the groups invested $0.02.

For every 1,000 email subscribers, the average organization has 355 Facebook fans, 132 Twitter followers, and 19 Instagram followers. The report showed that the nonprofits surveyed saw an average of 29 percent growth of support on Facebook over the year and a 25 percent growth of support on Twitter.